Chapter 41 Notes Animal Nutrition - PowerPoint Presentation

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Chapter 41 Notes

Animal Nutrition

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Nutritional Requirements

The flow of energy into and out of an animal can be viewed as a “budget”

- most of the energy taken in is used to produce ATP to power resting metabolism and temperature regulation

- excess ATP can be used for biosynthesis

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Nutritional Requirements

In humans, the liver and muscle cells store energy in the form of glycogen.

If glycogen stores are full, the excess is usually stored as fat.

When fewer calories are taken in than used, fuel is taken out of storage deposits and oxidized.

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Nutritional Requirements

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Nutritional Requirements

Feedback mechanisms regulate fat storage and use

- an increase in adipose tissue increases leptin levels in the blood

- high levels of leptin cue the brain to depress appetite and to increase muscular activity and body-heat production

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Nutritional Requirements

In addition to providing fuel for ATP, a diet must also supply the raw materials needed for biosynthesis.

- organic precursors (carbon skeletons)

-

essential amino acids

-

essential fatty acids

-

vitamins

and

minerals

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Nutritional Requirements

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Food Types and Feeding Mechanisms

Even though animals are classified as

herbivores

,

carnivores

, or

omnivores

, they are

opportunistic feeders

in that they eat foods outside of their main dietary categories

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Food Types and Feeding Mechanisms

There are four main groups that animals can be separated into based on the way they feed

Suspension-feeders

: animals that sift food particles from water

Substrate-feeders

: animals that live on their food source, eating their way through food

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Food Types and Feeding Mechanisms

Fluid-feeders

: animals the survive by sucking nutrient-rich fluids from a living host

Bulk-feeders

: animals that eat relatively large pieces of food

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Overview of Food Processing

The four main stages of food processing are ingestion, digestion, absorption, and elimination

Ingestion

: the act of eating

Digestion

: the process of breaking food down into molecules small enough for the body to absorb

-

enzymatic hydrolysis

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Overview of Food Processing

Absorption

: the animal’s cells take up small molecules such as amino acids and simple sugars

Elimination

: undigested material passes out of the digestive compartment

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Overview of Food Processing

Digestion occurs in specialized compartments to reduce the risk of self-digestion

Intracellular digestion

: use of food vacuoles where hydrolytic enzymes break down food without digesting the cell’s cytoplasm

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Overview of Food Processing

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Overview of Food Processing

Extracellular digestion

: the breakdown of food outside cells

Many animals with simple body plans have

gastrovascular cavities

- these function in both the digestion and distribution of nutrients throughout the body

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Overview of Food Processing

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Overview of Food Processing

Most animals have digestive tubes extending between two openings- complete

digestive tracts

or

alimentary canals

- the advantage is that animals can ingest additional food before earlier meals are completely digested

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Overview of Food Processing

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The Mammalian Digestive System

The oral cavity, pharynx, and esophagus initiate food processing

- the presence of food in the oral cavity triggers the release of

saliva

.

-saliva contains

amylase

, the enzyme that hydrolyzes starch

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The Mammalian Digestive System

The stomach stores food and performs preliminary digestion

- the stomach secretes

gastric juices

and mixes them with food by a churning motion

- also present in the gastric juices is

pepsin

, an enzyme that begins the hydrolysis of proteins

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The Mammalian Digestive System

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The Mammalian Digestive System

The small intestine is the major organ of digestion and absorption

- the first 25 cm of the small intestine is called the

duodenum

. Here chyme from the stomach is mixed with juices from the pancreas, liver, and gall bladder

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The Mammalian Digestive System

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The Mammalian Digestive System

- the pancreas produces hydrolytic enzymes and an alkaline solution that acts as a buffer to neutralize the low pH of the chyme from the stomach

- the liver produces

bile

. Bile does not contain enzymes, but acts as detergents that aid in the digestion and absorption of fats

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The Mammalian Digestive System

Carbohydrate digestion

:

- begins with salivary amylase in the oral cavity

- pancreatic amylase hydrolyzes starch, glycogen, and other polysaccharides into disaccharides

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The Mammalian Digestive System

Protein digestion

:

- enzymes in the duodenum break apart proteins into amino acids

-

trypsin

and

chymotrypsin

break the peptide bonds

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The Mammalian Digestive System

Fat digestion

:

- hydrolysis of fat is a special problem because fat molecules are insoluble in water

- bile salts work through

emulsification

so that

lipase

can break down fat molecules

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The Mammalian Digestive System

Most absorption occurs in the small intestine

- s.i. has a large surface area due to the folding of the lining into

villi

- each villus has many microscopic appendages called

microvilli

which increase the rate of absorption

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The Mammalian Digestive System

- in the core of each villus is a net of capillaries and a small vessel of the lymphatic system called the

lacteal

- nutrients are absorbed across the intestinal epithelium and then across the epithelium of the capillaries or lacteals

- nutrients then flow into the bloodstream

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The Mammalian Digestive System